Organic gellation agents

ABSTRACT

The present invention generally relates to the formation of organic gels by dissolving organic gelling agents in organic solvents. The aryl cyclohexanol gelling agents employed in this invention are not structurally related to previously known gellation agents and they exhibit potent gellation activity, for example, from 0.2-5%, by weight, of gelling agent is able to immobilize a variety of organic solvents. The gels formed range from optically transparent to slightly translucent, and complete fluidity can be restored by either increasing the temperature (reversible) or by chemical treatment (irreversible).

BACKGROUND OF THE INVENTION

Gels are generally formed when attractions between molecules facilitatethe formation of an extensive three-dimensional network that traps thesolvent between "strands" of the network. For example, organicgel-foxing materials may have multiple polar functionalities that allowfor network formation by hydrogen bonding.

Agents able to immobilize organic solvents as gels have many potentialapplications. For example, these materials could be used to gel marineoil and chemical spills and assist in their containment and recovery,particularly with a water insoluble gelling agent. Additionally, theremay be applications in chemical synthesis because reactions occurring ina gelled solvent may proceed at different rates or with different regio-or stereo-selectivity as compared to similar reactions in traditionalsolvents. These materials might also be employed in the development ofnew chromatographic stationary phases or semi-permeable membranes, inthe transfer of organic liquids, or in the application of solvents, likemethylene chloride, in a gelled state (U.S. Pat. No. 4,986,936; U.S.Pat. No. 4,479,825). For example, it would be advantageous to gelorganic liquids, such as fuels, industrial solvents and organicadditives, prior to transportation, either for further use or disposal,in a gelled state. This gelled state would be more stable, lessvolatile, and easier and safer to contain in the event of an accident enroute. One may even speculate as to the stabilization of organic liquidsunder near-zero gravity conditions of vehicles in earth orbit.

Alternatively, it would be beneficial to develop components for use inthixotropic materials. For example, compounds that gel organic liquids,such as acetone, toluene, benzene, ethyl acetate, alcohols, andmethylene chloride, would be useful in varnish and paint remover tofacilitate its storage, transportation and application. Wood stains areoften benefitted by a gel formulation and could be prepared using themethods, compositions and compounds of the present invention. Theformulation and/or stabilization of organic emulsions should also beaided by the new gel compositions of the present invention.

Unfortunately, compounds which cause gellation of organic solvents areunused and often complex and expensive to prepare. For example,Kobayashi describes the use of various compounds, including sorbitolderivatives, as gelling agents. (JP 05,320,617, JP 04,368,389, JP04,352,787, and JP 03,281,684). JP 53,124,595 describes the gellation ofan organic liquid by the incorporation of a gel of an alicyclic alcohol,which contains the alicyclic alcohol and the condensation product of anaromatic aldehyde and a polyhydric alcohol.

The present invention alleviates many of the problems inherent in theprior art by providing water insoluble organic gelling agents that arerelatively simple and inexpensive to prepare.

SUMMARY OF THE INVENTION

The present invention encompasses a method for gelling an organic liquidcomprising dissolving an effective amount of an aryl cyclohexanolgelling agent in an organic liquid, and cooling the resultant mixture toform a gel.

As used herein the term "dissolving" refers to causing the solid gellingagent to pass into solution such that the organic liquid and the gellingagent are in one liquid phase. It is envisioned that heating may benecessary to facilitate dissolution of the gelling agent.

As used herein the phrase "aryl cyclohexanol gelling agent" refers to achemical composition of a 1-aryl cyclohexanol that facilitates thegellation of the organic liquid. Ineffective gelling agents appear tocrystallize immediately rather than form gels. The cyclohexanol and arylmoieties may be further functionalized in aryl cyclohexanol gellingagents of the present invention.

In fact, some functionalization of the cyclohexanol is required becausethe stereochemistry at the hydroxyl carbon of the cyclohexanol isimportant. The 1-aryl group should be in the axial position. Therefore,it may be necessary for a sterically bulky alkyl group to be so situatedon the cyclohexyl ring, to force the 1-aryl group into the axialposition, i.e. by forcing the cyclohexanol ring to stay in oneconformation. For example, preferred gelling agents of this inventionemploy tertiary alkyl groups in the 4 position trans to the alcoholfunctionality. Although there may be some electronic constraints on thetypes of alkyl groups that may be employed, it is envisioned that theprimary factor in choosing the alkyl group will be employing a groupthat forces the cyclohexanol ring into the proper conformation. Thus,trans-1-aryl-4-tert-butylcyclohexanols are particularly preferred forpracticing the present invention but other bulky alkyls may be found toperform as well. It is also envisioned that other structurally relatedalcohols with similarly positioned hydroxyl and aryl groups may also beuseful in practicing the present invention.

The functionalization of the 1-aryl group is also important. Forexample, several closely related cyclohexanols were surprisinglyineffective gelling agents. For example, compounds with para-fluoro orpentafluoro substituted aryls were effective gelling agents whilecompounds with para-methoxy, para-methyl, para-trifluoromethyl andseveral other related substituted aryls were ineffective as gellingagents. While not limiting the present invention by any theory, it ispostulated that this difference in gelling activity is due to acombination of steric and electronic substitutional effects. Whileseveral effective aryl groups (phenyl, para-fluorophenyl andpentafluorophenyl) have been prepared and tested, other phenylsubstituents may be found by following the simple methods of the presentinvention involving dissolution of prospective gelling agents andcooling the solution to form a gel. Compounds that are ineffective atgelling tend to crystallize upon cooling.

More preferred gelling agents aretrans-1-phenyl-4-tert-butylcyclohexanol (compound 2),trans-1-(para-fluorophenyl-4-tert-butylcyclohexanol (compound 3), andtrans-1-(pentafluorophenyl)-4-tert-butylcyclohexanol (compound 4), withtrans-1-phenyl-4-tert-butylcyclohexanol being the most preferred.

An "effective amount" of the gelling agent refers to the amount ofgelling agent required to cause the gellation of the organic liquid. Theexact amount required will depend on the nature of the organic liquidand the gelling agent as well as the temperature to which the mixture iscooled. A wide variety of concentrations are effective. An upper limiton the amount is the saturation point of a particular liquid, i.e. thesolubility of the gelling agent in the hot organic liquid, becauseover-saturation may result in crystallization of the gelling agent outof the mixture upon cooling. Additionally, there is a tendency forconcentrated solutions (>5%) to crystallize rapidly. It is envisionedthat the most preferred gels will contain very small amounts of gellingagent, e.g., from about 0.2 to about 5% by weight.

A wide variety of organic liquids, including, but certainly not limitedto, diethyl ether, toluene, heptane, methylene chloride, and ethylacetate, can be gelled with the gelling agents of the present invention.While ethanol dissolved trans-1-Phenyl-4-tert-butylcyclohexanol(Compound 2), upon cooling trans-1-Phenyl-4-tert-butylcyclohexanolcrystallized, rather than inducing gel formation. Many organic liquids,including organics not typically considered as solvents may by gelled bygelling agents of the present invention, e.g., such as alpha-pinene. Theorganic liquid should be capable of dissolving the aryl cyclohexanolgelling agent and gelling upon cooling, rather than resulting incrystals of gelling agent. The organic liquid can be a mixture ofseveral organic chemicals and may also contain a mixture of dissolvedchemicals. Generally, more polar liquids tend to require larger amountsof gelling agents and have lower "melting points".

The amount of cooling required for the formation of the gel depends onthe nature and amount of the aryl cyclohexanol gelling agent and thecomposition of the organic liquid. Generally, the mixture should becooled below the melting point of the gel. Additionally, lowertemperatures tend to be required to gel more polar solvents and thosemixtures with lower percentages of gelling agent.

A preferred embodiment of the present invention is where the arylcyclohexanol gelling agent is from about 0.2 to about 5 percent byweight of the mixture. Concentrations of gelling agent above 5% byweight have not been generally operable due to problems with the gellingagent's solubility and its tendency to crystallize. As used herein, theterm "mixture" is used to refer to the physical combination of thegelling agent and the organic liquid. This mixture can be homogeneous,heterogeneous or gelatinous.

Another embodiment of this invention encompasses the compositions ofmatter comprising trans-1-(para-fluorophenyl)-4-tert-butylcyclohexanolor trans-1-(pentafluorophenyl)-4-tert-butylcyclohexanol.

Another embodiment is a gel comprising an aryl cyclohexanol gellingagent and an organic liquid that is capable of dissolving the gellingagent. A preferred embodiment of the present invention employs a1-aryl-4-alkylcyclohexanol as the gelling agent. More preferred gels usetrans-1-phenyl-4-tert-butylcyclohexanol,trans-1-(para-fluorophenyl-4-tert-butylcyclohexanol, andtrans-1-(pentafluorophenyl)-4-tert-butylcyclohexanol as the gellingagent, with trans-1-phenyl-4-tert-butylcyclohexanol being the mostpreferred.

More preferred gels of this invention contain from about 0.2 to about 5percent cyclohexanol gelling agent by weight of the mixture and employdiethyl ether, toluene, heptane, methylene chloride, or ethyl acetate asthe organic liquid.

Another embodiment of the present invention encompasses a method forgelling a first organic liquid incapable of dissolving an arylcyclohexanol gelling agent but miscible with a second organic liquidthat can dissolve said agent. This method comprises dissolving aneffective amount of an aryl cyclohexanol gelling agent in the secondorganic liquid, mixing this solution with a first organic liquid, andcooling the resultant mixture to form a gel. This method is envisionedas being useful in the prevention, clean-up, containment, transfer, andrecovery of chemical and oil spills.

As used herein the term "first organic liquid" refers to any organicliquid incapable of substantially dissolving the cyclohexanol gellingagent, for example, mineral oil. The phrase "second organic liquid"refers to liquids that dissolve the gelling agent and gel upon cooling,such as the organic solvents mentioned above.

A preferred embodiment employs 1-aryl-4-alkyl-cyclohexanols as thegelling agent, with trans-1-phenyl-4-tert-butylcyclohexanol,trans-1-(para-fluorophenyl-4-tert-butylcyclohexanol, andtrans-1-(pentafluorophenyl)-4-tert-butylcyclohexanol being morepreferred and trans-1-phenyl-4-tert-butylcyclohexanol being the mostpreferred.

A preferred embodiment of this invention encompasses the method forgelling a chemical substance wherein the gelling agent is from about 0.2to about 5 percent by weight of the mixture and the first organic liquidis diethyl ether, toluene, heptane, methylene chloride, or ethylacetate.

The present invention may be used as a method of impeding undesiredevaporation of an organic solvent that dissolve aryl cyclohexanols byemploying aryl cyclohexanol gelling agents. The method involvesselecting a particular sample of such an organic solvent possiblysubject to conditions allowing undesired evaporation, dissolving aneffective amount of an aryl cyclohexanol gelling agent in said sample toform a solution, and cooling the solution to form a gel. Evaporation ofthe solvent from the gel is thereby impeded.

The present invention also includes a method of impeding leakage of asolvent that dissolves aryl cyclohexanols from a container by employingan aryl cyclohexanol gelling agent. This comprises selecting a sample ofa solvent held or to be held in a container, dissolving an effectiveconcentration of an aryl cyclohexanol gelling agent in the solvent toform a solution and cooling the solution after enclosure in a containerto form a gel. Leakage of the solvent from any pores or openings in thecontainer is thus impeded.

DESCRIPTION OF THE DRAWINGS

FIG. 1. Synthesis of Gelling Agenttrans-1-Phenyl-4-tert-butylcyclohexanol (Compound 2).

FIG. 2. Correlation of melting point with weight percent of the gellingagent trans-1-phenyl-4-tert-butylcyclohexanol (Compound 2) in □ diethylether, ⋄ toluene, ◯ heptane, Δ dichloromethane, and ethyl acetate.

FIG. 3. Modifications of the aromatic ring of compound 2 studied. Of themodified components, only the two ring fluorinated compounds 3 and 4 (inbox) were active gelling agents.

FIG. 4. Comparison of Compounds 2 (⋄), 3 (□) and 4 (◯) for ability togel heptane. Unresolved compound 2 (+) was 51% trans and 49% cis, andthe weight percent was based on the amount of the trans isomer present.

FIG. 5. Gel melting point versus weight percent of para-fluoro gellingagent, compound 3, in heptane (□), toluene (⋄), diethyl ether (◯),dichloromethane (Δ), and ethyl acetate .

FIG. 6. Gel melting point versus weight percent of pentafluoro gellingagent, compound 4, in toluene (□), heptane (⋄), and methylene chloride(◯).

FIG. 7. Gel melting point versus weight percent of gelling agentcompound 2 (□), compound 3 (⋄), and compound 4 (◯) in toluene.

FIG. 8. Gel melting point versus weight percent gelling agent compound 2(□) and compound 3 (⋄) in diethyl ether.

FIG. 9. Gel melting point versus weight percent of gelling agentcompound 2 (□), compound 3 (⋄), and compound 4 (◯) in dichloromethane.

FIG. 10. Gel melting point versus weight percent gelling agent compound2 (□) and compound 3 (⋄) in ethyl acetate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The organic gelling agents of the present invention offer manyadvantages over those previously reported because of their differentstructural, physical and chemical properties. The alcohols such astrans-1-phenyl-4-tert-butylcyclohexanol (compound 2) are considerablysmaller than known gelling agents (see FIG. 1). Thus, the new materials-aryl cyclohexanol gelling agents- have higher volatility and can be madeto evaporate or sublime under the proper conditions, i.e. vacuum andheating. The smaller size may provide different gellation kinetics (rateof gel formation). The new materials are also almost certainly lesswater soluble than the known gelling agents which may make them moresuitable for use in water-containing environments.

In practicing the present invention, the 1-aryl group of thecyclohexanol gelling agent should be in the axial position. For example,compound 2 is an active gelling agent while compound 1 is not (see FIG.1). The preferred gelling agents of this invention employ tertiary alkylgroups in the 4 position trans to the alcohol functionality. Thus,trans-1-aryl-4-tert-butylcyclohexanols are particularly preferred forpracticing the present invention but other bulky alkyls may be found toperform as well.

In addition, tertiary benzylic alcohols such as compound 2 undergodehydration rapidly in the presence of suitable acids. This couldprovide a method of quickly and irreversibly de-gelling these materials.It is unlikely that the previously known materials could accommodatesuch an irreversible process. Gels made with various solvents andcompound 2 were subjected to conditions of low pressure. Solventevaporation was very slow from the gel as compared to the ungelledsolvent. This can reduce undesired solvent loss in an economically andenvironmentally sound manner. The flow of solvents from a gel, or theflow of the gel, in a container with pores or openings is alsosubstantially slower than the flow of ungelled solvent from such acontainer.

EXAMPLE 1

During the preparation and the isolation of alcohols 1 and 2 by additionof a phenyl Grignard reagent to 4-tert-butylcyclohexanone, the formationof a gel was observed. (See FIG. 1). Following separation of the twoisomers, the gellation behavior was traced entirely to alcohol 2.

The gels are generally prepared by dissolving alcohol 2 (a solid) into agiven solvent using heat; upon cooling, a slightly translucent gel isobserved. The gels will re-liquify if warmed sufficiently, with theprocess being entirely reversible. Alcohol 2 crystallizes very slowlyfrom a gel if the process is initiated with a small amount of solid. Thepreparation of alcohols 1 and 2 by the same or similar routes has beenreported many times, though no reference to gellation behavior has beenreported.

Alcohol 2 causes gellation in a variety of organic solvents such as,e.g., heptane, ethyl acetate, toluene, dichloromethane and ether, thoughdifferent concentrations were required in each solvent to achievegellation at a given temperature. FIG. 2 illustrates the general trendobserved, that more polar solvents require higher amounts of the agentin order to gel. The agent was dissolved in the solvent at variousweight percents and the solution cooled to a gel. The melting pointswere then observed upon slow warming.

EXAMPLE 2

The gellation activity of a variety of structurally related moleculeswas investigated. Compounds containing a total of seven differentaromatic rings were prepared and screened for gellation behavior. (SeeFIG. 3). Only certain ring-fluorinated aromatics (compound 3 and 4)exhibited gellation activity, again with only one of the two isomersbeing active. Compounds 2 and 3 are exhibit relatively comparablegelling activity in heptane and were more effective gelling agents thancompound 4 in heptane (see FIG. 4). Gelling activity is also effected byweight percent of agent and the nature of the solvent (see FIG. 5 andFIG. 6). For example, the higher the weight percent, the higher themelting temperature. In addition, the formation of gels with highermelting temperatures is seen with more apolar organic liquids. Thesensitivity to organic liquid is exhibited by employing toluene as theorganic liquid because in toluene all compounds 2, 3 and 4 exhibitdifferent gelling activities, as opposed to heptane where compounds 2and 3 exhibit comparable gelling activity. In all cases, opticallytransparent gels were observed. In addition, compound 3 exhibits extremeresistance to crystallization.

EXAMPLE 3

When unresolved compound 2, i.e., 51% trans and 49% cis was utilized, itwas noted that, when calculated according to how much of the transisomer was present, the gelling capacity was almost identical to that ofthe resolved trans isomer. This was indicated in FIG. 4 (see "+" in FIG.4.). This indicates that although the cis isomer was not an effectivegelling agent, it did not inhibit gellation by the trans isomer.

EXAMPLE 4 The Gel Melting Point Behavior Employing Compounds 2, 3 and 4

FIG. 7 shows the melting point versus weight percent of the gellingagent for various gels formed from toluene and compounds 2, 3 or 4. FIG.8 shows the gel melting point versus weight percent of the gelling agentfor compounds 2 and 3 in diethyl ether. FIG. 9 shows the gel meltingpoint versus weight percent of the gelling agent for compounds 2, 3 and4 in dichloromethane. FIG. 10 shows the gel melting point versus weightpercent of gelling agent for compound 2 and compound 3 in ethyl acetate.

EXAMPLE 5

These gelling agents may also gels liquids in which they do notdissolve. This has potential application in the clean-up, containmentand storage of chemical spills, particularly those containing oils, forexample. For example, compound 2 was dissolved in diethyl ether. Thissolution was then added to mineral oil and cooled to form a gel, eventhough compound 2 is not soluble in mineral oil.

While the compositions and methods of this invention have been describedin terms of preferred embodiments, it will be apparent to those of skillin the art that variations may be applied to the systems, compositions,methods and in the steps or in the sequence of steps of the methodsdescribed herein without departing from the concept, spirit and scope ofthe invention. For example, it will be apparent that certain agentswhich are chemically, compositionally and functionally related may besubstituted for the agents described herein where the same or similarresults may be achieved. All such similar substitutes and modificationsapparent to those skilled in the art are considered to be within thespirit, scope and concept of the invention as defined by the appendedclaims.

The following references are incorporated in pertinent pan by referenceherein for the reasons cited in the above text.

BIBLIOGRAPHY

U.S. Pat. No. 4,986,936.

U.S. Pat. No. 4,479,825.

JP 53,124,595.

JP 05,320,617.

JP 04,368,389.

JP 04,352,787.

JP 03,281,684).

What is claimed is:
 1. A method for gelling an organic liquid comprising:dissolving an effective amount of trans-1-phenyl-4-tert-butylcyclohexanol, trans-1-(para-fluorophenyl)-4-tert-butylcyclohexanol, or trans-1-(pentafluorophenyl)-4-tert-butylcyclohexanol in an organic liquid and cooling resultant mixture to form a gel.
 2. The method of claim 1, wherein the concentration of the dissolved 1-aryl-4-tert butylcyclohexanol is from about 0.2 to about 5 percent by weight of the mixture.
 3. The method of claim 1, wherein the organic liquid is diethyl ether, toluene, heptane, methylene chloride, or ethyl acetate.
 4. A method for gelling an organic liquid comprising:dissolving an effective amount of trans-1-phenyl-4-tert-butylcyclohexanol in an organic liquid; and cooling the resultant mixture to form a gel.
 5. A gel comprising a trans-1-phenyl-4-tert-butylcyclohexanol, trans-1-(para-fluorophenyl)-4-tert-butylcyclohexanol, or trans-1-(pentafluorophenyl)-4-tert-butylcyclohexanol agent and an organic liquid capable of dissolving said agent.
 6. The gel of claim 5, wherein the concentration of the 1-aryl-4-tert-butylcyclohexanol agent is from about 0.2 to about 5 percent by weight of the gel.
 7. The gel of claim 5, wherein the organic liquid is diethyl ether, toluene, heptane, methylene chloride, or ethyl acetate.
 8. A gel comprising a trans-1-phenyl-4-tert-butylcyclohexanol agent and an organic liquid capable of dissolving said agent.
 9. A method of gelling a first organic liquid incapable of dissolving an aryl cyclohexanol gelling agent but miscible with a second organic liquid capable of dissolving said agent, the method comprising:dissolving an effective amount of trans-1-phenyl-4-tert-butylcyclohexanol, trans-1-(para-fluorophenyl)-4-tert-butylcyclohexanol, or trans-1-(pentafluorophenyl)-4-tert-butylcyclohexanol gelling agent in a second organic liquid; mixing this solution with a first organic liquid; and cooling the resultant mixture to form a gel.
 10. The method of claim 9, wherein the concentration of the 1-aryl-4-tert-butylcyclo-hexanol gelling agent is from about 0.2 to about 5 percent by weight of the mixture.
 11. The method of claim 9, wherein the second organic liquid is diethyl ether, toluene, heptane, methylene chloride, or ethyl acetate.
 12. The method of claim 9, wherein the first organic liquid is mineral oil.
 13. A method of gelling a first organic liquid incapable of dissolving an aryl cyclohexanol gelling agent but miscible with a second organic liquid capable of dissolving said agent, the method comprising:dissolving an effective amount of trans-1-phenyl-4-tert-butylcyclohexanol gelling agent in a second organic liquid; mixing this solution with a first organic liquid; and cooling the resultant mixture to form a gel. 